Question

Chemical changes___ involve the breaking and making of chemical bonds. 1)sometimes 2)always. 3) never

Answer 1

Answer:

Chemical changes always involve the breaking and making of chemical bonds.

Explanation:

In chemical changes, the atoms regroup to form new substances. As the first law in Thermodynamic says, "energy cannot be created or destroyed"

Answer 2

Answer:

Option 2 Always is the Answer

Explanation:

Breaking of bonds requires energy. Absorption of energy takes place to break a bond.

Formation of a bond results in the release of energy.

Hence breaking of bonds is an endothermic process and formation of a bond is exothermic.

The enthalpy of a reaction or the Heat energy of a reaction is given by  

$\Delta H=E_p-E_r$

$E_p$ stands for energy of products

$E_r$ stands for energy of reactants

If $E_p>E_r$  then ∆H will be Positive and the reaction is Endothermic

If $E_p<E_r$ then ∆H will be Negative and the reaction is Exothermic